Plot summary
Katrina falls ill, and blames Henry for poisoning her. Turning him and the Horseman against each other, she escapes and collapses in the woods, and is eventually brought to the hospital. Abbie and Ichabod manage to extract her before Henry's men can, and they study her condition. Henry is revealed to be in league with the Hellfire Club, a sect of Moloch worshippers, and Katrina's "illness" turns out to be the early stages of pregnancy. Ichabod blames the Horseman, but Katrina defends him. Henry's men raid the archives, and they retreat to the church.
Despite Henry's actions, Katrina remains convinced that he will save her, as he is still her son. Ichabod confronts Henry at the asylum, learning that the baby is in fact Moloch himself. After learning that the concentrated light of the aurora borealis can exorcise Moloch, Ichabod and Abbie use an enchanted prism stolen from the Club to destroy the poison.
Credits
Adapted from Wikipedia contributors, Sleepy Hollow season 2. HTML formatting and reference markers removed.